A Canadian interface design firm accused Mozilla of stealing user interface (UI) elements for a development tool in the browser maker's Jetpack project, which aims to simplify add-on making.

MetaLab of Victoria, British Columbia, leveled the charges Tuesday when the 11-person firm's founder, Andrew Wilkinson, blogged about the similarities between his company's designs and those posted by Mozilla for FlightDeck, a Jetpack editor.

"What they did was pretty ridiculous," Wilkinson said in an interview today, arguing that there is a distinction between being inspired by another designer's work, and copying it outright. "There's a difference between inspiration versus ripping something off," he said. "The measurements of the graphic elements [Mozilla took from us] were the exact same, the very same pixels. When someone takes your images from the server hosting them, that's crossing the line."

Mozilla apologized to MetaLab Wednesday. "While the design direction being implemented does not utilize these design elements, we inadvertently included the early mockups in our blog post and video announcing the next phase of development for the Jetpack SDK," said Mozilla in a blog post of its own. "We sincerely apologize to MetaLab for incorporating design elements from their web site in our early mockups and for posting them publicly without proper attribution."

Yesterday, Mozilla declined to comment further about the plagiarism charges.

"Usually, we just shrug off these kinds of things, have a good laugh and then get in touch privately," said Wilkinson. "But we were so shocked by all this. We made a big stink because it was so ridiculous."

Wilkinson was referring to a proposal MetaLab submitted last November to Mozilla for crafting the FlightDeck user interface. "Mark [Nichols of MetaLab] spent an hour on the phone with Daniel Buchner and Aza Raskin [of Mozilla], going through our proposal in detail," said Wilkinson in his blog post Tuesday. Buchner told MetaLab Dec. 27 that Mozilla had decided not to hire the firm for the project.

What rubbed MetaLab the wrong way, said Wilkinson, was the thought that Mozilla had been put off by the fee the firm had wanted for the work, but then grabbed FlightDeck's design elements from MetaLab's site anyway. "The guy who's the project lead for Jetpack was so involved in that proposal," said Wilkinson, talking about Buchner, who is the Mozilla project manager for Jetpack.

"The Mozilla situation was the perfect storm. They know who we are, they are a massive company, and we had even bid on the project. It was too much," added Wilkinson in a follow-up blog post late Wednesday.

Even so, "there are no hard feelings," Wilkinson said today. He credited Mozilla CEO John Lilly with acknowledging the problem within hours via Twitter, and said he had spoken with the Mozilla team on the phone. "They were very apologetic," he said.

But he also slammed critics who had argued that MetaLab made a mountain out of a molehill because MetaLab's design elements were used only in a mockup and not in a live build of FlightDeck.

"Imagine if Microsoft had previewed the SDK for their Windows phone platform and all the marketing materials, press releases, and video demos showed elements of Apple's iPhone UI," said Wilkinson in the Wednesday blog. "Of course, there's a reason for everything: 'The iPhone UI was only used during development to help us scope out the feature set' [or] 'It was one of our interns, we had no idea' [or] 'It was never going to be released.' People would start throwing things."

Mozilla shipped the first milestone release of the Jetpack SDK (software developer kit) Tuesday. The company has removed the mockups that used MetaLab content from its site, and has updated the video demonstrations and screenshots to reflect the SDK's actual content.